1. Field of the Invention
The present invention generally relates to an apparatus for controlling operation for starting an internal combustion engine such as typified by the engine for an automobile or a motor vehicle or the like. More particularly, the present invention is concerned with an engine starting control apparatus which can ensure a proper starting performance for the internal combustion engine with a fuel injection quantity of a lean air-fuel ratio while reducing positively and significantly a discharge quantity of hydrocarbons (HC) and others upon starting of the operation of the internal combustion engine.
2. Description of Related Art
In general, in the internal combustion engine for a motor vehicle equipped with a fuel injection system and an ignition system which are of electrically or electronically controlled type, cranking operation is carried out by using an electric starter motor in an engine starting phase until complete explosion has been brought about to enable the electronic control of the fuel injection and the ignition on a cylinder-by-cylinder basis. In the course of the cranking operation, the fuel injection quantity and the ignition timing are set to respective predetermined values in dependence on the engine rotation number or speed (rpm) detected after the cranking has been initiated.
In that case, it is desired or required to ensure appropriate starting performance for the internal combustion engine while rendering the exhaust gas components to be favorable by reducing or suppressing the discharge quantity of hydrocarbons and others (hereinafter also referred to simply as the HC discharge quantity).
By way of example, in the starting control apparatus for the internal combustion engine described in Japanese Patent Application Laid-Open Publication No. 343914/1999 (JP-A-11-343914), the fuel injection control for the individual cylinders of the internal combustion engine in the engine starting phase is carried out during the suction stroke, wherein when the engine rotation number or speed (rpm) increases excessively, the ignition timing is correctively retarded to thereby lower the engine rotation speed (rpm).
More specifically, in the engine starting phase, the time duration for which the intake valve is held open (i.e., suction stroke) is set relatively long for allowing the fuel required for the combustion to flow into the combustion chamber defined internally of the cylinder so that even in the case where the engine starting operation is performed at a low temperature, the air-fuel ratio of the air-fuel mixture can be set to a value lying within a range in which combustion of the air-fuel mixture can occur without fail. In this way, the HC discharge quantity can be reduced in the engine starting phase.
However, in the hitherto known engine starting control apparatus such as disclosed in the publication cited above, the quantity of fuel charged at the predetermined ignition timing is set to a predetermined value as required until the complete explosion takes place. In other words, concentration of the fuel of the air-fuel mixture as injected is not always set to a necessary minimum value. Consequently, the intended object (i.e., suppressing the HC discharge quantity to a possible minimum in the engine starting phase) unfortunately remains to be achieved satisfactorily. In other words, the conventional technique such as disclosed in the above-mentioned publication does not always represent practically effective resolution for reducing the HC discharge quantity in the engine starting phase.
As is apparent from the above, in the conventional engine starting control apparatus such as typified by the one disclosed in Japanese Patent Application Laid-Open Publication No. 343914/1999, the fuel injection quantity and the ignition timing are set or maintained at respective predetermined values upon starting of the cranking operation in dependence on the engine rotation speed detected after the start of the cranking operation until it is decided that the complete explosion can be brought about. In other words, the fuel is injected in a sufficient quantity capable of triggering the complete explosion.
To say in another way, a same quantity of fuel is supplied at a same ignition timing to all the individual cylinders of the engine in which combustion takes place sequentially over a time period from the initial explosion up to the complete explosion. Such being the circumstances, there arises a problem that the air-fuel mixture may unwantedly be charged with an unnecessarily rich air-fuel ratio (i.e., with a high fuel concentration) until the output torque capable of triggering the complete explosion is made available, rendering it practically impossible to suppress or reduce the HC discharge quantity with high reliability in the engine starting phase.
In the light of the state of the art described above, it is an object of the present invention to provide a starting control apparatus for an internal combustion engine which apparatus is capable of ensuring proper or improved starting performance with a fuel injection at a lean air-fuel ratio while reducing positively the HC discharge quantity in the engine starting phase with enhanced reliability.
In view of the above and other objects which will become apparent as the description proceeds, there is provided according to a general aspect of the present invention a starting control apparatus for an internal combustion engine including an intake pipe for supplying an air-fuel mixture containing air and a fuel to the engine having a plurality of cylinders, a throttle valve mounted internally of the intake pipe for adjusting flow rate of intake air fed to the engine, a fuel injection valve for charging the fuel into the cylinder of the engine, a spark plug provided in association with each of the plural cylinders of the engine for igniting the air-fuel mixture charged into the cylinder, various types of sensors for detecting operating state of the engine, and a control unit for controlling the fuel injection valve and the spark plug in dependence on the operating state of the engine upon starting of operation thereof. The control unit is comprised of a combustion stroke discriminating means for discriminatively identifying combustion strokes taking place sequentially among the plural cylinders, wherein the fuel injection quantity supplied to the individual cylinders of the engine and the ignition timing for burning the charged fuel are set variably for the individual combustion strokes, respectively, upon starting of operation of the engine.
In a preferred mode for carrying out the invention, the control unit may include a counter for counting the number of the combustion strokes taking place sequentially among a plurality of cylinders from a time point at which cranking is started upon starting of operation of the internal combustion engine, wherein the fuel injection quantity and the ignition timing for each of the cylinders may be set on the basis of the number of the combustion strokes.
In another preferred mode for carrying out the invention, the control unit may include a storage for storing control quantity map data bearing correspondency to the fuel injection quantity and the ignition timing, respectively, with the number of the combustion strokes being used as parameter with a view to setting the fuel injection quantity and the ignition timing by looking up the control quantity map data, wherein the map data value for the fuel injection quantity may be set variably so that the control quantity increases or alternatively decreases in dependence on increase of the number of the combustion strokes.
By virtue of the arrangements described above, appropriate or proper engine starting performance can be realized with the fuel quantity of a lean air-fuel ratio while reducing positively the HC discharge quantity in the engine starting phase.
In yet another mode for carrying out the invention, the various types of sensors mentioned previously should preferably include a water temperature sensor for detecting cooling water temperature of the internal combustion engine, wherein the control unit should preferably be so designed as to set the fuel injection quantity and the ignition timing on the basis of the cooling water temperature.
In still another mode for carrying out the invention, the various types of sensors mentioned above should preferably include a rotation sensor for detecting a rotation number (rpm) of the engine, wherein the control unit should preferably be so designed as to set a correcting quantity for the ignition timing in dependence on the rotation number of the engine.
In a further mode for carrying out the invention, the control unit should preferably include a storage for storing correcting quantity map data bearing correspondency to the control quantity for the ignition timing as a function of change of rotation number of the engine, wherein the control unit should preferably be so designed as to set a correcting quantity for the ignition timing by looking up the correcting quantity map data to thereby set finally the ignition timing determined by adding or subtracting the correcting quantity to or from a reference value of the ignition timing.
With the arrangements described above, the engine starting performance as well as the exhaust gas quality can further be improved in the engine starting phase.
The above and other objects, features and attendant advantages of the present invention will more easily be understood by reading the following description of the preferred embodiments thereof taken, only by way of example, in conjunction with the accompanying drawings.